1. Field of the Invention
The present invention relates to a compact disk-interactive system which is a home multimedia appliance utilizing a compact disk.
2. Description of the Related Art
Compact disk-interactive (hereinafter referred to as CD-I) systems digitally store and reproduce from five inch optical disks texts, graphics, data, etc. in combination with high quality audios, still pictures, or motion pictures. A CD-I system enables a user to use the above-mentioned information in a conversational manner.
A prior art CD-I system is illustrated in FIG. 1. Referring to FIG. 1, the prior art CD-I system comprises a central processing unit (CPU) 11 for controlling and executing the operation of the system, an erasable and programmable read only memory (EPROM) 12 including a compact disk real time operating system (CD-RTOS) as the operating system of the CD-I system which enables a user's program input, and a nonvolatile random access memory (NVRAM) 13 for preserving data in case of power-off.
The prior art CD-I system is also provided with a host interlace peripheral controller (HIPC) 14 for controlling the interface between the CPU 11 and peripheral devices, a compact disk drive (CD drive) 15 for storing or reading information on a compact disk, a compact disk interface controller (CDIC) 31, a video output section 20, an audio output section 30, and a system bus 16 composed of an address bus and a data bus required to transmit addresses and data among the above-mentioned devices. Any CPU of a 68000 series manufactured by Motorola Co. Ltd. may be employed in the CD-I system.
The CD-RTOS is a multiprogramming operating system for a CDI system utilizing a compact disk. The CD-RTOS performs real time multiprogramming in the foreground, while performs batch processing in the background. Also, according to the CD-RTOS, a program input from the disk and a program output thereto are automatically performed. The CD-RTOS further provides basic functions such as resource allocation, interrupt processing, scheduling, input/output management, program management, etc. required for a user to configure a specific real time software.
As illustrated in FIG. 1, the audio output section 30 is provided with an audio signal processor (ASP) 32, and an audio digital-to-analog converter (ADAC) 33. The video output section 20 is provided with a video decoder and system controller (VDSC) 21, a RAM 22 for storing the operation data of the system, and a video digital-to-analog converter (VDAC) 23.
The operation of the prior art CD-I system as constructed above will be described in detail.
When a compact disk is inserted in the CD drive 15, data is read from the disk by an optical pickup device (not illustrated) in the CD drive 15, and then it determines whether the read-out data is audio data, video data, or program data. If the read-out data is determined as compact disk-digital audio (CD-DA) data which corresponds to a pure audio signal, it is not sent to the CPU 11, but is directly sent to the ASP 32 under the control of the CDIC 31. The ASP 32 processes the data and outputs a digital audio signal to the ADAC 33. The ADAC 33 converts the digital audio signal to an analog audio signal.
If the data read out from the disk is determined as data including video data and program data, such as compact disk-graphic (CD-G) data, compact disk-extended graphic (CD-EG) data, CD-I data, photo-compact disk (photo-CD), etc., the CDIC 31 sends the video data and the program data to the CPU 11 through the system bus 16. In this case, the video data is processed through the VDSC 21 and the VDAC 23 to be outputted as a video signal, and the program data is processed through the HIPC 14 to be properly sent to the peripheral devices.
Specifically, if the read-out data is CD-G data or CD-EG data, which includes both audio data and video data, the audio data is processed in the audio output section 30 and the video data is decoded by means of the CD-TROS stored in the EPROM 12. The VDSC 21 receives the decoded video data, and accordingly, outputs a digital video signal composed of red (R), green (G), and blue (B) color signals with predetermined color rates, respectively. The digital video signal is then converted to an analog video signal through the VDAC 23.
Meanwhile, if the read-out data is CD-I data, the audio data is generally processed by the audio output section 30. However, in case of a sound map mode for optionally outputting sound by the user, the audio data is stored in the RAM 22 through the VDSC 21 and is then read therefrom when required. The video data is sent to the RAM 22 through the VDSC 21 by means of direct memory access (DMA). In this case, if one sector of the RAM 22 is fully occupied, the VDSC 21 first decodes the data format of the video data and determines the coding type thereof. The coding type of the CD-I video data may be one among a color look up table (CLUT) type coding, a run length (RL) coding, and a delta YUV (DYUV) coding. The video data is then decoded in accordance with its coding type to be outputted as a digital video signal composed of R, G, and B color signals. The output digital video signal is converted to an analog video signal through the VDAC 23. At this time, data movement and proper data process are performed by the CD-RTOS stored in the EPROM 12.
The DMA is a method of performing direct data input/output between a peripheral device and a memory, not by way of a CPU, and thus is mainly used in a system having a large amount of input/output data. The DMA can increase the calling rate of the system.
However, the prior art CD-I system employs a 68000 series CPU and thus has no compatibility with software programmed using an 80 series code. For instance, though the 68000 series CPU identifies the instruction code of "COPY" with "10010001", the 80 series CPU may not do so, and thus the same instruction code cannot be used in common between the two CPUs. Consequently, the prior art CD-I system cannot reproduce a compact disk-read only memory (CD-ROM) programmed using the 80 series code.